Circuit arrangements for originating electric currents or potentials for signal or control purposes



Sept. 29, 1959 F. MITTAG 2,906,942

CIRCUIT ARRANGEMENTS FOR ORIGINATING ELECTRIC CURRENTS 0R POTENTIALS FORSIGNAL OR CONTROL PURPOSES Filed Aug. 2, 1955.

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1 3 L2 L1 A 5 U fnvemon- E) N 6 F. MITTAG ATTORNEY United States PatentCIRCUIT ARRANGEMENTS ELECTRIC CURRENTS OR POTENTIALS FOR SIGNAL ORCONTROL PURPOSES Fritz Mittag, Berlin-Friedenau, Germany, assignor toInternational Standard Electric Corporation, New York, N.Y., acorporation of Delaware FOR ORIGINATING The invention has for its objectto provide an arrangement by means of which it is possible in a simpleand reliable manner to originate an electric current or potential, forsignaling or control operations. Electromagnetic relays, excited byshort pulses, have been used in such arrangements. If, however, thecontrol pulses for these relays be too small to operate them, the pulseduration being too short or the amplitude of the pulses too small, suchdevices are not suitable for use. In these cases electron tubes havebeen used. Preferably, the tubes employed to this end are gas-filled,these becoming ignited by the pulse and then carrying a relativelystrong current.

In many cases the use of electron tubes is undesirable because theirheating current must flow as long as they have to be ready for service,and because their life is limited in duration. It has also beenproposed, in order to originate an electric current for signaling orcontrolling purposes to use a magnetic amplifier and to provide meansfor varying momentarily its magnetic field.

According to the present invention an iron-core choke constitutes theinductance, or part thereof, of an electric oscillatory circuit whichwith the inductance in one of its two states is in resonance, or nearlyso, with an alternating voltage of a certain frequency. One of thesestates is the at-rest or normal condition, in which the iron-core chokeis uninfiuenced. The other or Working condition is that in which theinductivity of the choke has been altered by the field set up by acontrol device. The choke when in its at-rest state, is out of resonancewith the A.C. source. By changing the inductivity of the choke, thecircuit will be brought to be resonant to the voltage source. Thecurrent in the circuit now rises. Preferably it should be made to riseto such extent that the choke will become saturated. The increasedcurrent will continue after the magnetic influence on the choke has beenremoved, since current itself will have decreased the inductivity of thechoke. This current may then be used to initiate a control or signalingoperation.

It will be appreciated that the signal or control indication could alsobe initiated by bringing the oscillatory circuit from resonance tonon-resonance.

The invention will be more fully understood from the followingdescription, reference being had to the accompanying drawings in which:

Fig. 1 illustrates the mode of controlling an oscillatory circuit byinfluencing an iron-core choke thereof,

Fig. 2 shows a further development of the arrangement of Fig. 1,

Fig. 3 represents an embodiment which may be used for the storage ofsignals, and

Fig. 4 is a further embodiment of the invention.

In the embodiment according to Fig. 1 the oscillatory circuit is aseries circuit comprising an iron-core choke L, a capacity C, analternating voltage source E, and a resistance W. G. denotes a rectifierand R a relay connected across the resistance W. Capacity C can beshorted by a contact K.

In its normal or rest condition, the oscillatory circuit is out ofresonance with the frequency of the voltage source B. When a magnet M isintroduced into the magnetic field of choke L, the inductivity of itswinding is thereby so changed that the oscillatory circuit is thenresonant to the frequency of source E. The current in the oscillatorycircuit now rises to a maximum value so that a high voltage appearsacross the resistance W. This voltage is rectified by rectifier G andapplied to the energizing winding of relay R. The state so establishedwill not be changed when the magnet M is removed from the field of chokeL, because the change of the inductivity is now maintained by theincreased current in the oscillatory circuit. The normal or restcondition of the circuit will not be re-established until one of thefrequencydetermining elements, in this case the capacity C under thecontrol of contact K, is momentarily disconnected or shorted. Preferablythe circuit should be so dimensioned that in its working condition, thatis, in its condition of resonance, a saturation current will flow in thechoke L. Instead of a magnet, introduced into the field of the ironcorechoke L, a field produced by a continuous current may be employed.Moreover, the oscillatory circuit may be arranged as a parallel circuitin which case the condenser C would be connected across the choke L.

Where the arrangement is required to respond only to magnets or a fieldof a predetermined directivity, the iron-core choke may be provided witha permanent magnet arranged to cause premagnetization.

Such an arrangement is shown in Fig. additional permanent magnet M1 isprovided adjacent the choke L. The exciting magnet is again designatedM. If magnet M is so introduced into the field of choke L that theeffects of the magnets M, M1 are additive, the inductivity of coil Lwill thereby be decreased in a manner to bring about resonance of theoscillatory circuit. In the other case, however, in which the effect ofmagnet M is subtracted from that of magnet M1, the inductivity of L willbe increased, with the result that resonance will not occur. In this waythe polarity of magnet M will determine the control action to be broughtabout.

One application of the invention is in connection with devices whichserve to operate control or signaling arrangements in railways. In thiscase magnet M may be carried by a vehicle whilst the iron-core choke maybe mounted in the path of the vehicle, although in certain cases,particularly where the vehicles are manned, the reverse procedure isrecommended. By this means through the mutual movement between magnet Mand choke L a control or a signaling operation is initiated either onthe vehicle or at a point in its path, as the case may be. When soemployed, the arrangement will be of particular utility when thevehicles are not manned. The control action may thus serve to setrouting switches and/or to stop the vehicles. In particular this mode ofcontrol may be employed in pneumatic dispatch tube systems in order toset the routing switches thereof.

The arrangement may also be employed to store signals. A circuitrysuitable in this respect is shown in Fig. 3. Here the iron-core coil Lcomprises coils L1, L2, A short pulse applied to coil L2 acts to changethe state of the arrangement in the same manner as does the magnet M.The arrangement may be used to store a single pulse. The storage time isunlimited as long as the voltage source is eifective. In this case alsothe at-rest or normal state is established by varying one of theelements of the oscillatory circuit. Preferably, the capacity C may beshorted to that end by means of the contact K.

In the previously described arrangements the oscillatory circuit hasalways a small current flowing in it. Where this is undesirable, forexample in the case of 2. Here, an

3 indications required to be of high precision, the circuit of Fig. '4may -be employed to avoid this drawback.

The oscillatory circuit in {this embodiment comprises a condenser C, aresistance R, and the secondaries L1, L3 'o'f'th'e transformers iii,1'32. The rimaries are designated L2 v E denotes the voltage source. Theprimaries L2, L4 are connected inseries opposing. '1he secondaries L1,L3 are connected in-series aiding. Hence no voltage appears at theterminals i1, b because 'the voltages across the coils L1, L3 an'nuleach other. If now the magnetic field of one of thetransformers becomesaffected, as, for instance, through the approach of a permanent magnetM, then the inductivity of the coils L3, L4 decreases. -Consequently avoltage arises at the terminals a, b, since the voltages across L1, -L3are now different from each other. The voltage at a, b may assume such avalue that the current thenflowing through the coils L1, L3 acts to sochange the inductivity that the circuit becomes in resonance. Thereby acurrent is caused to flow in the oscillatorycircuit, and produces avoltage across resistor R. Such voltage continues to exist even thoughthe magnet M is removed and no longer influences the transformer U2,since the voltages across L1, L3 remain unequal. The at-rest or normalstate will not be reestablished until the oscillatory circuit isdisturbed by any one of its elements becoming altered. For example,condenser C may be shorted to that effect through closing the contact K.

It will be seen that with the arrangement not excited,

no current is flowing through resistance R while with the arrangementexcited the current flowing in it assumes its maximum value. Thearrangement thus. operates with great safety even if the sensitivity ofthe indicating instruments or of the relays to be controlled is small.

While I have described above the principles of my invention inconnection with specific apparatus, it, is to be clearly understood thatthis description is made only by way of example and not as a limitationto the scope of my invention as set forth in the objects thereof and inthe accompanying claims.

What is claimed is:

1. Circuit arrangement for originating an electric current or potentialfor signalling or control purposes, comprising an oscillatory circuit, asource of alternating current voltage of a predetermined frequency forexciting said circuit, an iron-core inductance connected to form part ofsaid oscillatory circuit the constants of said circuit "being so chosenthat it is normally non-resonant at said frequency a movable permanentmagnet adapted to be moved past said iron core inductance in juxtaposedrelation to it whereby a predetermined eifect is produced on theinductivity of said iron core inductance such as to bring saidoscillatory circuit from a condition of no e;

I resonance to resonance, means for 'ni'aififainifig s'aid "oscillatorycircuit iii-'said condition of resonance after the passage of saidpermanent magnet past said iron core inane-mace and switch means forrestoring'said oscillatory circuit to said condition of hou-resonance.

2. Circuit arrangement for originating an electric current or potentialfor signalling or control purposes comprising an oscillatory circuit, asource of alternating current of predetermined frequency eeupled to saidcircuit, an iron core choke of iectaiigular shape having on one limb aninductive winding which is connected to form part of said circuit theconstants of said circuit being so chosen that it is normallynon-'resonant'at said frequency,

. and a movable permanent bar magnet adapted to be moved past said chokejuxtaposed relation 'to the limb thereof opposite to saidfirst-mentioned limb whereby a predetermined efiect is produced on theinductance of said inductive winding dependent upon the direction ofpolarization of said bar magnet such as to bring said oscillatorycircuit from a condition of non-resonance to reson'ance, means itormaintaining said oscillatory circuit in Said C'OliditiOfi Of resonanceafter the passage Of Said bat magnet past said iron core inductance, andswitch means for restoring said oscillatory circuit to the condition ornon-resonance.

References Cited in the file of this patent UNITED STATES PATENTS2,330,242 Jewell July 10, 1945 2,427,213 Jewell Sept. 9, 1947 2,518,865Cartotto Aug. '15, 1950 2,5 0,2 4 Grandstatf July 10, 1915 1 2 ,653,254Spitzer et a1. Sept. 22, 1953 2,676,284- Bechberger Apr. 20, 19542,594,163 Sola Nov. 9, 1954 r 2,732,505 Walker et a1 Jan. 24, 1956FOREIGN PATENTS 379,711 Great Britain Sept. 5, 1952

